1. Field of the Invention
The present invention generally relates to conduits. The present invention generally relates to a conduit having a corrugated portion with a distance from a center of the conduit to a highest portion of a ridge that is substantially the same as the radius of an un-corrugated portion of the conduit. The present invention also generally relates to an apparatus and method for forming a corrugated conduit having a corrugated portion and an un-corrugated portion.
2. Description of Related Art
The use of conduits, such as tubes and pipe, is well known. For example, elongated hollow tubes may be used as heat exchange tubes. The use of tubes in heat exchangers is disclosed in various U.S. patents, including U.S. Pat. No. 2,365,688 to Dewey; U.S. Pat. No. 2,342,117 to Brown et al.; U.S. Pat. No. 2,499,901 to Brown; U.S. Pat. No. 2,797,554 to Donovan; and U.S. Pat. No. 4,162,702 to Andersson, which are incorporated by reference as if fully set forth herein.
In some applications, such as tube-in-shell type heat exchangers, tubes having a non-uniform outer surface have been proposed. For example, in U.S. Pat. Nos. 5,251,693 and 5,311,661 to Zifferer, both of which are incorporated by reference as if fully set forth herein, a heat exchange tube having a portion that includes corrugations is described. U.S. Pat. No. 4,377,083 to Shepherd; U.S. Pat. No. 4,514,997 to Zifferer; U.S. Pat. No. 2,110,965 to Singer; U.S. Pat. No. 2,378,729 U.S. Pat. No. 4,383,429 to Ceccacci, all of which are incorporated by reference as if fully set forth herein, also describe modifications of cross-sectional shape and/or area of conduits. U.S. Pat. No. 5,016,806 to Yapp et al., which is incorporated by reference as if fully set forth herein, describes the use of rollers to impart a desired shape to a tubular member.
Conduits may be formed of many different materials. Some conduits may be made of materials that are relatively soft (e.g., copper or aluminum). Wall thickness of some conduits may be relatively thin. A conduit made of a relatively soft material and/or a conduit having a relatively thin wall thickness may be corrugated using blades to press indentions in the conduit. Some conduits may be made of relative hard materials (e.g., carbon steel, stainless steel, titanium). Some conduits may have relatively a relative large wall thickness. The use of blades to form a corrugated conduit from a relatively hard material and/or from a conduit having a relatively large wall thickness may be difficult.
A pointing device may be used to form a conduit with a reduced diameter end. U.S. Pat. No. 5,311,661 to Zifferer, which is incorporated by reference as if fully set forth herein, describes a pointing device for forming a reduced diameter end portion in a conduit.